Perfluoroalkoxy-substituted propyl ethers of cellulose textile fiber and process of making



3,ti7,2i4 PERFLUGRGALKQXY-SUBSTETUTED PERGPYL ETl-ERS GF CELLULUSE TEXTILE FlBF-R ANE PROES 6F MAKING Raiph .l. Berni, .lohn E. McKelvey, and Ruth B. Benerito, New @rleans, La, assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Fiied .i'niy 6, 1959, Scr. No. 825,374 6 Claims. (Cl. 8-12ti) (Granted under Title 35, US. Code (1952), see. 266) A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to ceilulose ethers. More particularly, this invention relates to perfiuoroalkoxy-substituted propyl ethers of cellulose and processes for their production.

A primary object of the present invention is to provide novel cellulose ethers which are capable of being produced in the form of cellulosic textiles. A further object is to provide an etherification process that can suitably be employed to etherify hydroxyl group-containing cellulosic textile fibers with perfluoroglycidyl ethers without destroying the textile properties of the fibers. Another object is to provide perfiuo'roalkoxy-substituted propyl ethers of cellulose in textile fiber form wherein the etherification treatment is durable to alkaline soap washes in either aqueous or organic media.

Fluorocarbon compounds have been used in various ways in the prior art to impart oleophobic and hydrophobic surface characteristics to textiles. One method of accomplishing this is to prepare perfiuoroalkanoyl esters of the cellulosic textile. These cellulose esters possess good oiland water-repellency properties, but the ester linkages are rather easily hydrolyzed, particularly in the presence of alkaline soap washes, and consequently the chemical treatment is not durable to conventional aqueous laundering or to dry cleaning in the presence of alkaline soaps. Another disadvantage of prior art processes for treating cellulosic textiles with fluorocarbons is that rather high degrees of substitution (13.8.) of the cellulose are generally required to achieve the desired extent of oiland water-repellency.

We have discovered a Way to chemically treat cellulosic textile materials with fiuorocarbons to impart durable oiland water-repellency properties to the textiles, even at extremely low degrees of substitution of the cellulose of the textiles. The etherification treatment of the present invention is durable, not only to aqueous alkaline soap washes, but also to alkaline soap washes in organic media. Such durability of oiland water-repellency is not displayed by other types of perfluoro textile finishes presently available. The etherification process of the pres ent invention does not alter significantly the strength, color, appearance, hand, or fibrous form of the cellulosic material.

In general, in accordance with the present invention, a hydroxyl group-containing cellulosic material is etherified by reacting it with an etherifying agent comprising a perfiuoroglycidyl ether of the type represented by the following formula:

H CF3(CF2)nCHzO-CHz( J- CHz where n is an integer from O to 6. The etherifying agent reacts with a hydroxyl group of the cellulosic material through the oxirane oxygen ofsaid etherifying agent to 3,979,214 Patented Feb. 26, 1953 produce a perfluoroalkoxy-substituted propyl ether of cellulose of the following general type:

where n is an integer from 0 to 6, and Cell-O- represents the point of etherification of the cellulosic hydroxyl group. As the perfluoro moiety is removed or insulated from the ether linkages by one or more CH groups, the stability of the COC linkages is greatly enhanced.

Substantially any cellulosic material containing hydroxyl groups can suitably be employed in the present process. Illustrative examples of such materials include cellulose derived from cotton, flax, ramie and the like vegetable materials, wood cellulose, and regenerated cellulose such as viscose rayon and the like. In general, the cellulosic textile fibers, in the form of free fibers, slivers, yarns, threads or fabric, including the natural fibers and chemical modifications thereof which are produced by reactions in which the fibers retain unreacted hydroxyl groups as 'well as retaining their cellulosic textile prop erties, are preferred starting materials. The cellulose textile fibers in the form of spun textiles, i.e., yarns, threads or fabrics, are particularly suitable starting materials.

The perfiuoroglycidyl ethers employed as the etherifying agent in the process of the present invention can be conveniently obtained by reacting perfluoroalcohols of the type CF (CF CI-I OH, where n is an integer from 0 to 6, with epichlorohydrin in the presence of a basic catalyst. It is usually preferred to employ about 1 mole of epichlorohydrin for each mole of the perfluoroalcohol, and to use an excess (somewhat more than 1 mole) of sodium hydroxide as the catalyst. The reaction can be conveniently carried out in an aqueous medium at room temperature. The perfluoroglycidyl ethers can be isolated and purified using conventional procedures.

In carrying out the etherification process of the present invention, substantially any apparatus and handling techniques usually employed for the chemical treatment of cellulosic materials can be used. In the preferred etherification process of the invention, the cellulosic material to be etherified is first thoroughly wetted or impregnated with a solution of a strong alkali, such as sodium hydroxide. This impregnation can be accomplished by padding, that is, by passing the cellulosic material through the caustic solution and then through squeeze rolls to remove excess solution; or alternatively, by immersing the cellulosic material in the caustic solution and mechanically freeing the wetted material of substantially all of the liquid in excess of the amount retained by the porous portions of the material. It is generally preferred to employ mercerizing strength caustic solution (containing from about 12 to 20 weight percent of dissolved alkali hydroxide), and to impregnate the cellulosic material to a final wet pickup of about Following alkali-impregnation and adjustment to the desired wet pickup, the cellulosic material is reacted with the perfiuoroglycidyl ether etherifying agent. The periluoroglycidyl ether can be employed alone, without any solvent, or it can be used in conjunction with a suitable solvent. It is generally preferred to use the perfiuoroglycidyl ether without any solvent. Where a solvent is desired, substantially any inert solvent which is unreactive toward cellulose and is appreciably miscible with the etherifying agent can be used. The quantity of etherifying agent employed can be varied widely. Sufficient etherii'ying agent must be present to react with hydroxyl groups of the cellulose to give the degree of substitution desired by the operator. As the etherification reaction of the process of the present invention proceeds relatively slowly, it is generally preferred to use a severalfold excess of the etherifying agent over that theoretically required to etherify the available hydroxyl groups of the cellulosic material, in order to promote faster etherification. The treatment of the alkali-impregnated cellulosic material with the etherifying agent is preferably accomplished by contacting the cellulosic material with the etherifying agent at a temperature above the freezing point of the etherifying solution and below a temperature at which an undesirable amount of cellulose degradation occurs. It is usually preferred to conduct the etherification at a reaction temperature of from about 60 to 100 C. The contacting of the cellulosic material with the etherifying solution can be accomplished by immersing the cellulosic material in the solution. The cellulosic material can be reacted with the etherifying agent with which it is in contact by maintaining the material immersed in the solution at the reaction temperature.

The'extent of reaction, and thus the degree of substitution (i.e., the number of the three reactive hydroxyls per anhydroglucose unit which have been etherified) can be varied, primarily by varying the proportion of etherifying agentin contact with the cellulosic material and by varying the time and temperature of the etherification reaction. It is generally preferred to etherify the cellulose to a rather low'degree of substitution, between about a D8. of 0.01 and 0.10, as'the desired durable oiland water-repellency properties are imparted to the textile even at these low degrees of substitution. The time of reaction can be varied widely, depending on the particular etherifying agent used, the temperature at which it is reacted with the cellulosic material, and the DS, of the cellulose desired by the operator. In general, the preferred D.S.s can usually be achieved using reaction times of several hours at 60 to 100 C.

the procedures conventionally employed for the drying of cellulosic materials.

The following examples are given by way of illustrating certain details of the invention and not by way of limitation of the invention.

Example 1 1,1-dihydrcheptafluorobutyl glycidyl ether (O F7CH20OHEOg-;OHQ)

was prepared essentially according to the method of Brey and Tarrant [1. Am. Chem. Soc. 79, 653336 (1957)] from l,l-dihydroheptafluorobutanol, epichlorohydrin, and an excess of sodium hydroxide. The glycidyl ether, as prepared, had a purity greater than 80%, as determined by the oxirane oxygen method of Durbetaki [Anal Chem. 28, 2000 (1956)]. The impurities consisted of inert ma terials, principally the diether.

A 1.75 g. sample of 80 x 80 cotton fabric (scoured and bleached) was thoroughly impregnated with an aqueous sodium hydroxide solution containing 15 weight percent of dissolved sodium hydroxide by immersing the fabric in an excess of the solution for about 15 minutes, then removing the fabric and centrifuging it for about 5 minutes to remove excess alkali solution. The wet pickup of the fabric after centrifugation was 100%. The fabric was then wetted with and immersed in approximately 20 ml. of the above-described glycidyl ether preparation, and the mixture was allowed to react for 6 hours at 60-80 C., with shaking. The resultant etherified fabric was washed free of excess etherifying solution with methanol and acetone, the washing being continued for about 5 minutes until the treated fabric was odorless. The washed fabric was ironed dry to smooth its surface for subsequent testing for oil and water repellency.

The product was a fabric consisting essentially of heptafiuorobutoxypropyl ethers of cellulose in the form of textile fibers having a degree of substitution of 0.05 (as indicated by a fabric weight increase of 7.3% as a result of the treatment). It contained approximately 0.6% fluorine, as determined by the usual chemical analyses. The product had good tear strength, and its color, appearance, hand, and fibrous form were essentially unaltered. It possessed oiland water-repellent properties which were durable to a 20-minute boil in an aqueous, alkaline soap solution. The dry crease or wrinkle recovery angle of the fabric was 188 (warp+fill), and its wet crease recovery angle was 277 (warp-l-fill).

Example 2 1,l-dihydropentadecalluorooctyl glycidyl ether O1FaoHt0'-ornon-ona was prepared from 1,l-dihydropentadecafluorooctanel, epichlorohydrin, and sodium hydroxide, using essentially the same molar ratios and procedure described in Exampie 1. The glycidyl ether had a purity of 75%, as determined by the oxirane oxygen method of Example 1. The impurities consisted of inert materials, principally the diether.

A 1.75 g. sample of x 80 cotton fabric was treated with sodium hydroxide solution exactly as described in Example 1. Following centrifugation, the fabric was treated with about 20 ml. of the above-described glycidyl ether preparation at a temperature of C. for about 30 hours. The treated fabric was washed and ironed according to the procedure of Example 1.

The product was a fabric consisting essentially of pentadecafiuorooctoxypropyl others of cellulose in the form of textile fibers having a degree of substitutionof 0.01 (as indicated by a fabric weight increase of about 1% as a result of the treatment). The color, hand, appearance, and fibrous form of the product were essentially unaltered. it possessed excellent oil and water repellent properties which were durable to two 20-minute boils in an aqueous, alkaline soap solution, and a 30-minute boil in an aqueous soap and soda solution. These properties were also durable to soaking the fabric in a drycleaning solution (Stoddards solvent containing an alkaline drycleaning soap) for 15 minutes.

We claim:

1. A process of converting a cellulosic textile fiber containing free hydroxyl groups in the cellulose molecule to an etheriiled cellulosic textile fiber containing perfiuoroalhoxy-substituted propyl radicals attached to oxygen atoms of said cellulose molecules and possessing durable oiland water-repellency, comprising impregnating said hydroxyl group-containing cellulosic textile fiber with mercerizing strength caustic solution and then contacting the so-impregnated textile fiber with an excess of an etherifying agent of the group consisting of compounds represented by the formula where n is an integer from 0 to 6.

2. The process of claim 1 wherein the etherifying agent is l,l-dihydroheptafluorobutyl glycidyl ether.

3. The process of claim 1 wherein the etherifying agent is l,l-dihydropentadecafiuorooctyl glycidyl ether.

4. An .etherified cellulosic textile fiber wherein free 5 hydroxyl groups in the cellulose molecule are etherified by a perfiuoroalkoXy-substituted propyl radical having the formula CF (CF CI-I OCH Cl-I CH wherein n is an integer from 0 to 6.

5. An etherified cellulosic textile fiber wherein free hydroxyl groups in the cellulose molecule are etherified with the radical C3F7CH2OCH2CH2CH2.

6. An etherified cellulosic textile fiber wherein free hydroxyl groups in the cellulose molecule are efllerified the radical CqF 5CH -OCII CH2CH3.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS OF CONVERTING A CELLULOSIC TEXTILE FIBER CONTAINING FREE HYDROXYL GROUPS IN THE CELLULOSE MOLECULE TO AN ETHERIFIED CELLULOSIC TEXTILE FIBER CONTAINING PERFLUOROALKOXY-SUBSTITUTED PROPYL RADICALS ATTACHED TO OXYGEN ATOMS OF SAID CELLULOSE MOLECULES AND POSSESSING DURABLE OIL- AND WATER-REPELLENCY, COMPRISING IMPREGNATING SAID HYDROXYL GROUP-CONTAINING CELLULOSIC TEXTILE FIBER WITH MERCERIZING STRENGTH CAUSTIC SOLUTION AND THEN CONTACTING THE O-IMPREGANTED TEXTILE FIBER WITH AN EXCESS OF AN ETHERIFYING AGENT OF THE GROUP CONSISTING OF COMPOUNDS REPRESENTED BY THE FORMULA
 4. AN ETHERIFIED CELLULOSIC TEXTILE FIBER WHEREIN FREE HYDROXYL GROUPS IN THE CELLULOSE MOLECULE ARE ETHERFIED BY A PERFLUOROALKOXY-SUBSTITUTED PROPYL RADICAL HAVING THE FORMULA CF3(CF2)NCH2-O-CH2CH2CH2-, WHEREIN N IS AN INTEGER FROM 0 TO
 6. 